An important part of many environmental impact studies and other environmental analyses is the determination of the nature and quantity of wildlife in the area being studied. In order to perform population studies of many wildlife species, it is simply not enough to station a biologist or trained field technician in an area to monitor the wildlife being studied. This is because in many nature settings dense vegetation and/or inadequate light make it difficult for personnel to generate an accurate census of the wildlife. Moreover, the presence of survey personnel can disturb animal behavior and adversely affect survey results. Consequently, considerable effort has been devoted to developing other types of systems and methods to perform wildlife surveys.
Several types of electronic devices have been employed to aid in efforts to monitor wildlife. Some wildlife is monitored by capturing animals and attaching radio transmitters to their bodies. The signals emitted by the transmitters are monitored by one or more complementary receivers in order to determine the paths of the tracked animals. A disadvantage of the use of these transmitters is that they require the animal to be captured in order for transmitter to be harnessed to its body. This process of capturing animals so that they can be harnessed with a transmitter can be difficult, expensive, and dangerous. Scanning radars have been used to provide information on the location and velocity of airborne animals such as birds and small flying mammals. A limitation of these radars is that they have not proved particularly useful for locating animals located on the ground or perched in vegetation.
Owing to the inherent limitations of electronic monitoring devices, some wildlife studies are conducted by having trained personnel make audio surveys of the sounds, called vocalizations, made by wildlife within the study area. The vocalizations made by wildlife can provide information on the identity of its species, its age, gender, behavior, and home ranges. Wildlife which have been studied based on their vocalizations include species of birds, frogs, primates, wolves, coyotes, and elk. One limitation of such surveys is that they are inherently limited by a person's ability to hear, interpret, and remember sounds produced by the wildlife. Furthermore, as with the case of visual surveys, the presence of survey personnel can disturb animal behavior and subsequently affect survey results. Audio surveys, like visual surveys, can also be limited by the long hours and expense required to conduct thorough surveys.
There have also been some attempts to perform audio surveys by making recordings of the vocalizations made by the wildlife within a study area. An advantage of making these recordings is that once the recording equipment is in place, in can be left untended. This minimizes the human interference within the study site and reduces the field time personnel need to make the study. Another advantage of making these recordings is that they can be used to generate spectrographs of the vocalizations emitted by the wildlife. Trained personnel can then examine these spectrographs in order to determine the nature of the target wildlife that emitted the vocalizations that were captured by the recording apparatus. A disadvantage of many of these recordings though is that they only provide an indication that a particular species of wildlife is within the area being monitored, they do not provide an accurate indication of the location of the wildlife within the area. Thus, while such recording devices have proved useful tool for conducting wildlife survey, they are not without their own limitations.